Process of polymerizing acrylic and alkacrylic compounds



PRQCESS OF FOLYMEREG ACRWG 1 I t ALCRYLIC COOS Harry E. Dittmar, Wilmington, Bet, assignor, to

E. E. du Pont de Nernonrs & Company, Wilmington, Del, a corporation or Delaware No Drawing. Application y 21, 1935 serial No. 22.5'33- 17 cu. (erase-st) This invention relates to the production of are polymerized in emulsion or dispersed i'orm plastic materials by polymerization and more and the finished resin shows none of the above particularly to a new and improved method of disadvantages. A further object oi! the invenpolymerizing unsaturated organic compounds, tion is to provide a process for the polymeriza- 5 e. g., acrylic acid, methacrylic acid, their homotion of the unsaturated organic esters and more 5 logues, esters and other derivatives or mixtures particularly the alkyl esters of acrylicacid and thereof. alpha substituted acrylic acids, such as metha- The control of polymerization of the above gencrylic acid. or their homologues or derivatives or eral class of compounds is rendered diflicult since mixtures thereof by efiecting the polymerization it is often accompanied by considerable develof these compounds in the presence of starch or 10 opment of heat, and, as the temperature affects a starch ether as the dispersing or emulsifying the polymerization, it is difiicult, by the mere agent. Another object of the invention is to prodirect application of heat in the presence or abvide a process for the polymerization of unsatsence of suitable catalysts, to regulate the urated compounds dispersed or emulsified by polymerizationin order to obtain a fully polymerstarch or a starch ether such as methyl starch, 1 ized product in a suitable form. ethyl starch and the like, and subsequent to Various methods havebeen proposed to overpolymerization hydrolyziug the starch or starch come these difiiculties due to polymerization such, ether by any suitable means such as by subjectfor example, as the emulsion polymerization ing the polymer to the action of enzymatic processes described in British Patents 359,534 and hydrolysis. A more specific object of the inven- 20 374,436, and the granular polymerization process tion is to provide a process for the polymerizadisclosed in the copending U. S. applications of tion of the esters of acrylic and methacrylic acids Crawford et al., Ser. Nos. 749,500 filed. October while in emulsified or dispersed form and in the 22,1934, and 12,728 filed March 23,1935. When presence of methyl starch and the subsequent polymerizing in accord with the processes therehydrolysis of the methyl starch by the action of 25 in disclosed, an emulsifying agent or colloid is pancreatin. Other objects and advantages of the required in order to effect dispersion of the parinvention will hereinafter appear. ticles during their polymerization. After the I have found that monomeric polymerizable polymerization no attempt is usually made to compounds can be converted to high strength remove the colloid or other type of emulsifying polymers, when a dispersing or an emulsifying 30 agent employed and, due to the small percentage agent, such as starch or starch others, has been of these agents used, thorough removal would employed if the polymerized product, which conbe very difilcult. tains adsorbed to the individual particles of the Because of the residual emulsifying agent left polymer a considerable quantity of the starch in the polymerized product it has been found that or starch derivative, is treated in such a way that 35 w the value of the finished resin for many comthe starch or starch derivative present is hydromercial uses is greatly lowered. This is particulyzed and subsequent to its hydrolysis the hydrolarly true when the resin is molded or otherwise lysis product may be, and preferably is, washed shaped into a form which must have good from the polymerized product.

40 strength. Investigation has shown that; gener- The hydrolysis of the starch or starch deriva- 40 ally speaking, the resin produced by processes tives may be effected in any suitable manner, but not involving the use of emulsifying agents hithgenerally I prefer to treat the polymeric comerto used has considerably greater strength than pounds while in the dispersed or emulsified form, the resin obtained when the agent is present. and containing the starch or starch derivatives However, due to the desirable physical form of as dispersing or emulsifying agents, with ahydro- 45 the polymerized product when produced by the lyzing agent which is capable of converting the above processes the presence of residual emulstarch or starch derivatives to glucose or other sifying agent is practically unavoidable if this hydrolyzed derivative of the starch or starch form of product is produced. derivative. For this purpose I prefer to employ An object of the present invention is to prothe vegetable and animal amylases, which by 510 vide a polymerization process wherein a monomeans of enzymatic hydrolysis apparently hydromeric polymerizable compound is dispersed prior lyze the starch to the form of glucose, maltose, to polymerization by an improved emulsifying etc., which is readily removed by washing from agent. Another object of the invention is to prothe polymeric product. Specific types of hydrovide a polymerization process wherein compounds lyzing agents of this nature, which are particw, 55

hrly well adapted for use in my process, include, for example, pancreatin, 'amylopsin, pancreatic amylase, malt amylase, Taka-diastase, salivary amylase, leucocyte amaylase, barley amylase, potato amylase, cholam amylase, etc. 7

Owing to the infinite variety of starches available on the market, such as potato starch, corn starch, and like starches in general I have Iound that for best results ordinary starch is not as suitable as the starch ethers as a dispersing or emulsifying agent. This non-suitability is perhaps in no small part due to the varied chemical or physical constitution of these starches. Accordingly, I prefer to use modified starches such as the starch ethers either partially or fully etherified and of the starch ethers preferably the lower aliphatic ether starches, such, for example, as methyl starch, ethyl starch, propyl starch, and the like. For many purposes and particularly for the dispersion of such compounds as the alkyl methacrylates, such, for example, as methyl methacrylate, ethyl methacrylate, and the like, the methyl starches disclosed and claimed by O. R. Kreimeier and R. W. Maxwell in their pend-- ing U. S. application Ser. No. 720,076 filed April 11, 1934, are particularly well fitted These starch ethers comprise ethers having a low degree of alkylatlon in the neighborhood of from 0.02 to 0.75 mol of the alkylating agent per CeHroOs moi of starch.

When utilizing these starch ethers it is immaterial whether the monomeric compound be ultimately converted to the polymer as a gumlike material as the result of emulsion polymerization and ultimate coagulation, or as a granular or globular powder resulting from polymerization in granular form, for, in either instance, it will be found that if the starch ethers be used, and the latter subsequently hydrolyzed and removed, a resin having a strength equal to the strength of the polymeric resin per se is obtained.

I shall now illustrate by way of example several methods of conducting my process, but it will be understood that my invention shall not be restricted to the details therein given except as it may be limited by the claims appended hereto.

A. Example 1.-50 parts of acrylic acid ethyl ester are emulsified, by stirring, in parts of water containing 1% of potato starch. The emulsion is heated while stirring for 12 hours and from '75-85 C., under a reflux condenser. The emulsion is freed from the last traces of the unpolymerized ester by treating with steam and after cooling to approximately 40 C., 0.1% of pancreatin, based on the weight of polymeric ethyl acrylate, is. added; after about 15 minutes the product may be coagulated, if desired, by pouring' into a 4% solution of hydrochloric acid, after which it may be washed to remove the hydrochloric acid, whereupon a product is obtained soluble in acetone and the lower alkyl and aryl acetates.

Example 2.--50 parts of styrene and 50 parts of polyacrylic acid ethyl ester are emulsified, by stirring, in 200 parts of water in the presence of 1% of methyl starch. (The methyl starch was prepared by adding with stirring 2 kilograms of corn starch to 2 litres of water. To this dispersion grams of dimethyl sulfate were added together with 50 grams of sodium hydroxide and 1 litre of water during the course of 3'hours, the temperature being kept below 35 C. The product was filtered, washed with methanol and dried at 65 C.) The polymerization is effected at approximately room the neighborhood of approximately 20 days to give a practically completely polymerized product; 0.05% of pancreatln in added at 40 C., and

held for about 10 minutes. The product is coagulated by pouring into an aqueous 4% hydrochloric solution; it is then filtered and thoroughly washed with water. The product is soluble'in usual organic solvents, such as benzene and the lower alkyl acetates, and is considerably tougher than when the starch is not hydrolyzed.

Example 3.--A glass-lined jacketed kettle of 50 gallons capacity provided with a stirrer and a reflux condenser was charged with 25 gallons of water and 5 gallons of monomeric methyl methacrylate containing 1% (based on weight of monomer) of benzoyl peroxide and 0.8 cl 1% (based on monomer) of methyl starch containing .05 methyl groups per each Cal-11005 group. A T-shaped stirrer was revolved at 550 R. P. M., giving a fairly deep vortex and the temperature raised and maintained at approximately 80 C. After approximately 1 hour the polymerization was complete and a granular polymer separated and washed with distilled water. Upon molding under a temperature of C., and 3000 lbs/sq. in. a resin was obtained which when tested gave on an arbitrary scale a strength of approximately 6. The molding was also hazy due apparently to the presence of the methyl starch.

B. Another batch of methyl methacrylate was polymerized as directed in Example 3A and prior to washing was subjected to the enzymatic hy drolysis of 0.02% of pancreatin (based on the weight of polymer present) for 15 minutes at 40 C.; it was then washed and dried as in 3A. The molded resin on the same arbitrary scale as in BA had a strength of 22 and was brilliantly clear and wholly transparent.

The treatment of the emulsified or dispersed polymer to destroy the ultimate weakening effect temperatureandrequircsin attributed to the starch or starch derivative may be carried out in many ways. Usually I prefer to add the vegetable or animal amylase directly to the aqueous or other liquid containing the dispersed or emulsified polymer. The amylase acts at room temperature but more rapidly at temperatures of 40 C., the time of reaction requiring in the neighborhood of from 5-25 minutes.

My process is applicable primarily to the production of polymeric compounds which are normally solid at ordinary temperature. Among the additional compounds which can be advantageously polymerized by my process are: esters, nitriles, and amides of acrylic acid, e. g., ethyl, methyl, propyl, butyl, and the higher acrylates; the esters, nitriles and amides of methacrylic acid, e. g. methyl, ethyl, propyl, butyl, and amyl methacrylate s; the higher alkyl methacrylates such as nonyl, decyl, and lauryl methacrylates, the primary, secondary, and tertiary. straight or branch chain saturated or unsaturated alcohol esters of methacrylic or the other alkacrylic acids; and the acids per se, i. e., acrylic acid and methaorylic acid. The above compounds may be prepared by any suitable process such, for example, as the processes disclosed in U. S. Patents 1,980,483, filed November 3, 1932; 1,993,089, filed November 10, 1933; 2,013,648, filed December 30, 1933, and 2,041,820, filed May 5, 1934. These compounds may, if desired, be polymerized alone or ally to the formula MCI-1:011:5 In many instances the vinyl type compounds may also be advuhtageously polymerized in accord with my process. I have stressed the advantage of utilizing my 5 process for the polymerization of compounds which give solid resins principally because molded products so prepared from such resins have better strength. It is to be understood, nevertheless, that my process may likewise be used, if desired, for the production of polymeric compounds which are not solids under normal conditions. The advantages of additional strength will not generally be obtamed, altho that advantage may be ofiset by homogeneity and/or clarity of the finished 5 resin.

In the present invention when reference is made to polymerization in the dispersed state to produce a polymer in the emulsified form or as a granular productit will be appreciated that conditions, such as quantity of dispersing agent, temperature, type, and amount of stirring, etc., are a prerequisite to the preparation of the polymer in the form desired. The starch or starch ether of my invention is used, as has been described, to

afiect the dispersion no matter what may be its degree.

From a consideration of the above specification it will be appreciated that many improvements and modifications of the details therein given may be made without sacrificing the advantages derived from the invention.

I claim:

1. A process for the polymerization of methyl methacrylate in which the monomeric methyl 'methaorylate is polymerized while in an aqueous polymerizing medium in the presence of methyl starches the dispersing agent, the step which comprises removing methyl starch by treating the dispersed polymerized methyl methacrylate 40 with from 0.05 to 0.5% of panel-satin based on the weight of the polymeric resin.

2. In a process for'polymerizing a monomeric methyl methacrylate while dispersed in water to give a polymer in the granular form the step which comprises effecting the dispersion with methyl starch as the dispersing agent and obtaining the polymeric product in granular form.

3. In a process or" polymerizing a monomeric alkacrylic acid in an emulsified state the steps which comprise emulsifying the alkacrylic acid with methyl starch as the dispersing agent, polymerizing the emulsified acid, adding an agent that will hydrolyze starch, hydrolyzing the methyl starch and subsequently coagulating and washing the product.

4.111 a process of polymerizing a monomeric methyl methacrylate in a granular form the steps which comprise dispersing the methyl methacrylate with starch ether as the dispersing agent,

polymerizing the dispersed ester, adding an agent that will hydrolyze starch, hydrolyzing the starch ether andsubsequently coagulating and washing the product.

5. In a process of polymerizing a monomeric methyl methacrylate in a granular form the steps which comprise dispersing the methyl methacrylate with methyl starch as the dispersing agent, polymerizing the dispersed ester, adding an 'agent that will hydrolyze starch, hydrolyzing the methyl starch and subsequently coagulating and washing the product.

6. Process which comprises subjecting methyl methacrylate to polymerizing conditions while dispersed in water containing a dispersing agent selected from the group consisting of starch and starch others to give a polymeric ester in granular form: on completion of the desired polymerization. adding a hydrolyzing agent whereby the dispersing agent is rendered water soluble; and

separating the thus hydrolyzed dispersing agent 5 from the polymer as an aqueous solution.

7. Process which comprises subjecting methyl methacrylate to polymerizing conditions while dispersed in water containing a. dispersing agent selected from the group consisting of starch and 1 starch others; on completion of the desired polymerization, adding an enzymatic hydrolyzlng agent whereby the dispersing agent is rendered water soluble; and separating the thus hydrolyzed dispersing agent from the polymer as an 15 aqueous solution.

8. Process which comprises subjecting methyl methacrylate to polymerizing conditions while dispersed in water containing a dispersing agent selected from the group consisting of starch and 20 starch others; on completion of the desired polymerization, adding pancreatin whereby the dispersing agent is rendered water soluble; and separating the thus hydrolyzed dispersing agent from the polymer as an aqueous solution. I

9. Process which comprises subjecting methyl methacrylate to polymerizing conditions while dispersed in water containing a dispersing agent selected from the group consisting of starch and starch others; on completion of the desired poly- 30 merlzation, adding an enzymatic hydrolyzing agent whereby the dispersing agent is rendered water soluble; and thereafter separating and water-washing the polymeric product.

10. In a process for polymerizing monomeric 35- alkacrylic acid compounds while dispersed in water to give a polymer in granular form, the steps which comprise effecting the dispersion with methyl starch, which has been alkylated with not more than 0.75 mol of allwlating agent 40 per CeHroUs a mol of starch, as the dispersing agent and obtaining the polymer in granular form.

11. In a process for polymerizing monomeric methyl ,methacrylate while dispersed in water to 45 give a polymer in granular form, the steps which comprise effecting the dispersion with a starch ether which contains from approximately 0.02 to 0.75 mol of alkylating agent per CaHmOs mol of starch, as the dispersing agent and ob- 50 taining the polymer in granular form.

12. In a. process for polymerizing monomeric methyl methacrylatev while dispersed in water to give a polymer in granular form, the steps which comprise effecting the dispersion with methyl 55 starch containing from approximately 0.02 to 0.75 mol of methylating agent per CoHroOs mol of starch and obtaining the polymer in granular form.

13. In a process for polymerizing monomeric 60 acrylic acid esters while dispersed in water to give a polymer in granular form, the step which comprises effecting the dispersion with a starch ether as the dispersing agent."

14. In a process for polymerizing a. mono- 65 meric alkyl'methacrylate while dispersed in water to give a polymer in granular form, the step which comprises effecting the dispersion with a methyl starch as the. dispersing agent.

15. Process which comprises subjecting an al- 70 kyl methacrylate to polymerizing conditions while dispersed in water containing a dispersing agent selected from the group consisting of starch and starch others to gtve a polymeric ester in granular form, on completion of the de- 75 sired polymerization, adding a, hydrolyzing agent to the polymer whereby the dispersing agentis rendered water soluble: and separating the thus hydrolyzed dispersing agent from the polymer as an aqueous solution.

16. In a process for the polymerization of an alkyl methacrylate in which the monomeric sl- 1 kyl methacrylste is polymerized while dispersed in in aqueous polymerizing medium in the presence oi methyl starch as the dispersing agent, the step which comprises removing methyl starch by treating the polymerized alkyl meththe dispersion in the presence of a. starch ether m as the dispersing asent. g

' HARRY R. DITI'MAR. 

